Method and apparatus for evaluating electromagnetic hazard protection devices

Abstract

A method and apparatus which provide for measurement of embedded EMH, HIRF, or EMI (collectively referred to herein as EMH components), non-destructive measurement of embedded EMH components, component determination using only a simple current measurement; component determination without a priori knowledge of the range of values, the architecture of the test circuit that uses three MOSFET (or equivalent), switches, current measuring circuits, and suitable timing to accurately determine the component values, measurement of an embedded capacitor with relatively unknown parallel load resistance, and/or non-destructive measurement of R/C/TPD type components for any application.

1. A method for evaluating electromagnetic hazard protection on a unit under test (UUT), the UUT having a connector pin with at least one electromagnetic hazard (EMH) component connected thereto within the UUT, comprising:
 applying a sequence of voltage pulses which differ in pulse width to the connector pin; 
 measuring a current at the connector pin in response to each of a plurality of voltage pulses with different pulse widths included in the sequence of voltage pulses; and 
 determining a parameter of the EMH component based on the current measurements in response to each of the plurality of voltage pulses. 
 
     
     
       2. The method according to  claim 1 , wherein the EMH component is a terminal protection device (TPD) and the parameter is the TPD voltage. 
     
     
       3. The method according to  claim 2 , wherein the applying step comprises progressively increasing the pulse width of the voltage pulses within the sequence of voltage pulses to progressively increase a voltage produced across the TPD in response to each voltage pulse. 
     
     
       4. The method according to  claim 3 , wherein the determining step comprises comparing current measurements for successive voltage pulses included in the sequence in order to determine that the voltage produced across the TPD has reached the TPD voltage. 
     
     
       5. The method according to  claim 4 , wherein upon determining the voltage produced across the TPD has reached the TPD voltage, measuring the current at the connector pin during one of the voltage pulses and measuring the current at the connector pin immediately following the one of the voltage pulses, and calculating the TPD voltage based on the measured current during and immediately following the one of the voltage pulses. 
     
     
       6. The method according to  claim 1 , wherein the EMH component is an input series resistor and the parameter is the resistance of the input series resistor. 
     
     
       7. The method according to  claim 1 , wherein the EMH component is an electromagnetic interference (EMI) capacitor and the parameter is the capacitance of the EMI capacitor. 
     
     
       8. The method according to  claim 1 , wherein the method is non-destructive. 
     
     
       9. The method according to  claim 1 , wherein the method utilizes measurement of only the currents at the connector pin in order to determine the parameter. 
     
     
       10. The method according to  claim 1 , wherein a priori knowledge of a range of values within which the parameter is expected to exist is not applied. 
     
     
       11. A test apparatus for evaluating electromagnetic hazard protection on a unit under test (UUT), the UUT having a connector pin with at least one electromagnetic hazard (EMH) component connected thereto within the UUT, comprising:
 at least one functional circuit block for applying a sequence of voltage pulses which differ in pulse width to the connector pin; and 
 a measurement circuit for measuring a current at the connector pin in response to each of a plurality of voltage pulses with different pulse widths included in the sequence of voltage pulses. 
 
     
     
       12. The test apparatus according to  claim 11 , further comprising means for determining a parameter of the EMH component based on the current measurements in response to each of the plurality of voltage pulses. 
     
     
       13. The test apparatus according to  claim 12 , wherein the EMH component is a TPD and the means for determining is configured to calculate a TPD voltage of the TPD component. 
     
     
       14. The test apparatus according to  claim 12 , wherein the EMH component is an input series resistor and the means for determining is configured to calculate a resistance of the input series resistor. 
     
     
       15. The test apparatus according to  claim 12 , wherein the EMH component is an EMI capacitor and the means for determining is configured to calculate a capacitance of the EMI capacitor. 
     
     
       16. The test apparatus according to  claim 11 , wherein the measurement circuit comprises three functional circuit blocks for selectively providing a positive voltage pulse, ground voltage pulse and negative voltage pulse, respectively, with prescribed timing to create the sequence of voltage pulses. 
     
     
       17. The test apparatus according to  claim 11 , wherein the UUT includes a plurality of connector pins, and the test apparatus further comprises a matrix for controllably selecting which of the plurality of connector pins is evaluated by the at least one functional circuit block and the measurement circuit.